In a plastic molded article, more specifically in an automotive molded article, furthermore specifically in an automotive headlamp lens, an automotive headlamp PC lens requires characteristics such as high hardness or wear resistance. A paint composition for the hard coating of the automotive headlamp PC lens requires excellent productivity, adhesive property, water resistance, weatherability, etc. Further, the superior external appearance and productivity of the paint composition for automotive parts may be secured when the paint composition is coated by an air spray coating method.
Therefore, there is a need for an ultraviolet curable coating for plastic molded articles having excellent heat resistance and adhesive property, in response to recent environmental regulations and demands for improved productivity and a reduced manufacturing cost with a reduced cost for paint materials. Also, such coating is required to be applied with various methods such as a showering method, a curtain flow coating, etc., as well as an air spray method.
Korean Patent Publication No. 10-2007-0039742 discloses an example of paint compositions containing photocurable oligomers. However, a coating film as disclosed in the publication is formed with the paint composition having a multifunctional urethane acrylate oligomer alone. The coating film may show a crack or breakage due to the intermolecular contraction stresses within the coating film when the thickness of a dried coating film is 12 μm or greater, thereby causing the deterioration of the external appearance of the coating film, or decreasing the adhesive property of the coating film.
Korean Patent Publication No. 10-2011-0050952 discloses an ultraviolet curable paint composition having improved chipping resistance by using a combination of a multifunctional aliphatic urethane acrylate oligomer and a polycarbonate modified aliphatic urethane acrylate oligomer. However, the paint composition disclosed in the publication requires improvements in weatherability.